(a) Field of the Invention
The present invention relates to a hot dip galvanized steel sheet and a manufacturing method thereof. In detail, the present invention relates to a hot dip galvanized steel sheet having ultrahigh strength by using steel including a martensitic structure as a base material, and a manufacturing method thereof.
(b) Description of the Related Art
A hot dip galvanized steel sheet is inexpensive and has excellent corrosion resistance, so it is widely used for exterior parts of vehicles. A component of the vehicle such as a side impact beam uses the hot dip galvanized steel sheet since it requires corrosion resistance while maintaining strength against an impact provided from the outside. The strength of the hot dip galvanized steel sheet needs to be increased so as to protect vehicle occupants from accidents while making the vehicle light in weight.
Usage of the high strength steel for the vehicle and its occupants has recently increased because of an increase in demands regarding environment regulations, stability, and fuel efficiency. The high strength steel is generally used in two ways. The high strength steel is used to absorb an impact and disperse the force of the impact when a vehicle is in an accident. Dual phase (DP) steel and transformation induced plasticity (TRIP) steel have excellent toughness to absorb the impact under the condition of a head-on collision. However, the above-noted steels do not have sufficient strength to protect the occupants from a broadside collision or overturning. Therefore, in order to disperse the strong impact force without transformation, a material with excellent yield strength and tensile strength is needed.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.